Ophthalmic surgeons work within a very small operating field upon organs whose tissues are complex and delicate. Cuts made during surgery must be precise as to length, direction and depth, requiring surgical knives of unsurpassed sharpness and maneuverability.
Heretofore, most surgical knives available had blades held in fixed, non-adjustable relationship to the knife handle. Some blades were offset at a selected angle, while most blades extended straight out from the handle. Blades could be made with different configurations for particular cuts, but once these cuts were made, a new blade (or a new knife) had to be substituted for the remainder of the surgery.
Others have developed surgical knives with blades or blade holders that are angularly adjustable.
U.S. Pat. No. 4,672,964 (Dee) describes and claims a knife having a blade holder with a ball formed on one end which fits rotatably into a socket formed on a housing which then, in turn, is threadably attached to a knife handle. Mounted on the handle is a crank lever which moves a push rod toward the socket to contact the ball (and fix it in a selected position), or moves the push rod away from the ball to enable the ball (and, thereby, the blade holder) to rotate with respect to the handle. Changing the angle of the blade is an involved procedure: the surgeon must hold the handle with one hand and release the ball with the other by lifting the lever, reorient the blade, and re-clamp the ball by lowering the lever.
U.S. Pat. No. 4,788,976 (Dee, et al.) is a continuation-in-part of the '964 Dee patent, and adds to the '964 Dee patent a modified version of the crank lever mechanism used to clamp the ball and lock the blade in a selected position. Changing the blade angle still calls for significant manipulation of the knife adjusting mechanism.
U.S. Pat. No. 3,609,864 (Bassett) teaches and describes a surgical blade handle with a blade holder mounted to a ball. A knurled knob is threaded into the end of the handle, and a push rod extends within the handle from the knob to the ball. When the knob is threaded into the handle, the push rod contacts and clamps the ball at a selected angle, a two-handed procedure.
An arrangement very similar to that of Bassett is shown in Swiss patent 490,072 (Muller). A blade-and-ball assembly fits into a socket in a blade holder, and a handle is threaded into the blade holder until a handle projection contacts the ball.
U.S. Pat. No. 4,275,735 (Chutter) teaches and describes a blade holder within which a surgical blade may be selectively oriented and clamped. There is no capability for changing the angle of the blade during an operation without disassembling the holder and reinserting the blade. It appears that Chutter contemplates the prior setup of the knife rather than "on-the-fly" changes that may be required during surgery.
U.S. Pat. No. 3,922,784 (Prince, et al.) teaches and describes a swivel knife consisting of a handle and a blade holder clamped to the end of the handle. The blade holder allows the blade to be rotated about the axis of the blade holder, and the angle at which the blade holder is "skewed" with respect to the handle may be changed by loosening and retightening a thumb screw.
None of the prior art adjusting mechanisms described above allow the knife blade to be withdrawn into the handle to protect the blade when the knife is not being used, and to protect against accidental cuts to one who picks up the knife. It is particularly important to prevent accidental cuts during surgery, or accidental perforation of surgical gloves, where the danger of contamination in a bloody operating field is present.
The need exists, then, for a knife particularly suited to ophthalmic surgery with a blade that is angularly adjustable without the operation of mechanical locks or levers, or the removal and reinstallation of the cutting blade.
The need also exists for a blade angularly adjustable to selected, discrete angular positions.
The need also exists for a blade adjustment mechanism which holds the blade with a force firm enough to allow use in surgery, yet allows simple, one-handed adjustment of the blade angle during surgery.
The need also exists for a blade adjusting mechanism that will allow the blade to be moved simply to a straight position and then to be withdrawn into the knife handle when not in use to protect the blade and to prevent accidental cuts to one picking up the knife.